// This optional code is used to register a service worker.
// register() is not called by default.

// This lets the app load faster on subsequent visits in production, and gives
// it offline capabilities. However, it also means that developers (and users)
// will only see deployed updates on subsequent visits to a page, after all the
// existing tabs open on the page have been closed, since previously cached
// resources are updated in the background.

// To learn more about the benefits of this model and instructions on how to
// opt-in, read http://bit.ly/CRA-PWA

const isLocalhost = Boolean(
	window.location.hostname === 'localhost' ||
	// [::1] is the IPv6 localhost address.
	window.location.hostname === '[::1]' ||
	// 127.0.0.1/8 is considered localhost for IPv4.
	window.location.hostname.match(
		/^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
	)
)

export function register(config) {
	if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
		// The URL constructor is available in all browsers that support SW.
		const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href)
		if (publicUrl.origin !== window.location.origin) {
			// Our service worker won't work if PUBLIC_URL is on a different origin
			// from what our page is served on. This might happen if a CDN is used to
			// serve assets; see https://github.com/facebook/create-react-app/issues/2374
			return
		}

		window.addEventListener('load', () => {
			const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`

			if (isLocalhost) {
				// This is running on localhost. Let's check if a service worker still exists or not.
				checkValidServiceWorker(swUrl, config)

				// Add some additional logging to localhost, pointing developers to the
				// service worker/PWA documentation.
				navigator.serviceWorker.ready.then(() => {
					console.log(
						'This web app is being served cache-first by a service ' +
						'worker. To learn more, visit http://bit.ly/CRA-PWA'
					)
				})
			} else {
				// Is not localhost. Just register service worker
				registerValidSW(swUrl, config)
			}
		})
	}
}

function registerValidSW(swUrl, config) {
	navigator.serviceWorker
	.register(swUrl)
	.then(registration => {
		registration.onupdatefound = () => {
			const installingWorker = registration.installing
			if (installingWorker == null) {
				return
			}
			installingWorker.onstatechange = () => {
				if (installingWorker.state === 'installed') {
					if (navigator.serviceWorker.controller) {
						// At this point, the updated precached content has been fetched,
						// but the previous service worker will still serve the older
						// content until all client tabs are closed.
						console.log(
							'New content is available and will be used when all ' +
							'tabs for this page are closed. See http://bit.ly/CRA-PWA.'
						)

						// Execute callback
						if (config && config.onUpdate) {
							config.onUpdate(registration)
						}
					} else {
						// At this point, everything has been precached.
						// It's the perfect time to display a
						// "Content is cached for offline use." message.
						console.log('Content is cached for offline use.')

						// Execute callback
						if (config && config.onSuccess) {
							config.onSuccess(registration)
						}
					}
				}
			}
		}
	})
	.catch(error => {
		console.error('Error during service worker registration:', error)
	})
}

function checkValidServiceWorker(swUrl, config) {
	// Check if the service worker can be found. If it can't reload the page.
	fetch(swUrl)
	.then(response => {
		// Ensure service worker exists, and that we really are getting a JS file.
		const contentType = response.headers.get('content-type')
		if (
			response.status === 404 ||
			(contentType != null && contentType.indexOf('javascript') === -1)
		) {
			// No service worker found. Probably a different app. Reload the page.
			navigator.serviceWorker.ready.then(registration => {
				registration.unregister().then(() => {
					window.location.reload()
				})
			})
		} else {
			// Service worker found. Proceed as normal.
			registerValidSW(swUrl, config)
		}
	})
	.catch(() => {
		console.log(
			'No internet connection found. App is running in offline mode.'
		)
	})
}

export function unregister() {
	if ('serviceWorker' in navigator) {
		navigator.serviceWorker.ready.then(registration => {
			registration.unregister()
		})
	}
}
